Herpes viruses are a large group of intranuclear, double-stranded DNA viruses that are remarkably cagable of establishing a latent infection many years after a primary infection. The herpes virus group is responsible for such diseases as fever blister and keratoconjunctivitis (Herpes simplex virus type 1), venereal disease (Herpes simplex virus type 1 and 2), chickenpox (varicella) and shingles (Herpes zoster), cytomegalic inclusion disease (Cytomegalovirus), Marek's disease of chickens and infectious mononucleosis (Epstein-Barr virus).
Chickenpox (varicella) is one of the most common and highly communicable diseases and occurs primarily in childhood. A rash is observed generally over the entire body together with an attack of fever which occurs after an incubation period generally running between 14 and 17 days. The disease results in a mucular rash which may, in many cases, form pustules and, in extreme cases, leave scars. Other problems and complications may arise, for instance, in the case of undernourished children who may have necrotic dermal ulcer. Other complications such as central nervous system disturbance, myelitis and neuritis were known to occur as results from chickenpox.
A live varicella vaccine is known. U.S. Pat. No. 3,985,615, the disclosure of which is incorporated herein by reference, discloses a process for making a live varicella vaccine which comprises passaging the varicella virus in a guinea pig primary embryonic tissue cell at a temperature of from 32.degree. C. to 37.degree. C. until the virus is adequately attenuated.
Aqueous solutions of live virus vaccines are known to be unstable during storage. The conventional technique to reduce storage instability is to remove moisture by lyophilization. Conventional wisdom holds that the more moisture that is removed, the higher the storage stability of the live virus vaccine. Generally, live virus vaccines are lyophilized to moisture levels of less than about 1%.
Surprisingly, it has now been discovered that lyophilizing a live herpes virus vaccine to result in a moisture content within the range of from about 0.5% to about 8% results in increased storage stability to the live herpes virus vaccine. The increased storage stability permits the live herpes virus vaccine to be stored at 5.degree. C., i.e. in a refrigerator, rather than at -20.degree. C., i.e. in a freezer.